Still, it only heats my plants, so they don't seem to be too bothered by it. Both are fine heaters, just keep an eye on them, as you would with any heater. BTW, the Tronic seems to react much faster than my old heaters, as it uses an different method of control to conventional heaters. Hopefully that means a more stable temperature for my plants and fishies!Hi,I have ended up with 2 brand new heaters a fluval tronic 300w and a visi-therm 300w any one know which of these is the better. thanks in advance.